1. Field of the Invention
The present invention relates to a method of manufacturing a spindle motor in which an oil repellent film is formed by applying an oil repellent solution to a predetermined area of a rotating member and/or a stationary member constituting the spindle motor.
2. Description of the Prior Art
In recent years, in the spindle motor which is used for driving a recording medium such as a hard disc or the like, a hydrodynamic bearing utilizing a lubricating oil begins to be employed. The hydrodynamic bearing is provided, for example, with a hollow cylindrical sleeve having a bearing hole, a shaft fitted and inserted to the bearing hole at a micro gap in radial direction, and a lubricating oil filling the micro gap, and the sleeve and the shaft are supported so as to relatively rotate freely.
In this hydrodynamic bearing, there is a risk that the lubricating oil leaks out to an external portion of the hydrodynamic bearing along surfaces of the shaft and the sleeve. Accordingly, in order to prevent the lubricating oil from leaking out to the external portion of the hydrodynamic bearing, an oil repellent solution is applied to the surface of the shaft and/or the sleeve positioned near the hydrodynamic bearing, and an oil repellent film is formed thereon.
As an apparatus for coating the oil repellent solution, for example, the following oil repellent coating apparatus is disclosed in Japanese Patent Application Laid-open Publication No. 2001-232289. In other words, a deformed inner diameter portion in which an inner diameter is non-linearly changed in axial direction is formed in an inner peripheral portion of an annular bearing member. The oil repellent coating apparatus is provided with a coating head having a columnar projection portion including an opening portion in radial direction and fitted to the deformed inner diameter portion of the bearing member at a predetermined gap, and a seat portion with which a lower end surface of the bearing member is brought into contact, and automatically and evenly applies the oil repellent solution to the deformed inner diameter portion of the bearing member.
In this case, a recording medium driving apparatus using the spindle motor or another apparatus is promoted in a downsizing and a thin structure, and the spindle motor used in the apparatus is also promoted in a downsizing and a thin structure. Accordingly, an area in the spindle motor in which the oil repellent film should be formed for preventing the lubricating oil from leaking out is going to be further narrowed.
In particular, since the oil repellent solution is applied to a part of the predetermined area on the surface of the shaft and/or the sleeve, and is thereafter going to spread along the surface, the oil repellent solution runs over the predetermined area and the oil repellent film tends to be formed.
In the oil repellent coating apparatus described in Japanese Patent Application Laid-open Publication No. 2001-232289 mentioned above, it is possible to automatically apply the oil repellent solution to the deformed inner diameter portion in which the inner diameter is non-linearly changed. However, in the deformed inner diameter portion, it is impossible to control the area in which the oil repellent solution spreads so as to accurately form the oil repellent film in the predetermined area.